It was at Phnom Kulen, then known as Mahendrapura, that Jayavarman II had himself consecrated supreme ruler in 802 (a date that is regarded as marking the start of the Angkorian period), thereby instigating the cult of the devaraja. Although ancient temples are scattered here and elsewhere in the Kulen Mountains, none of these can be visited due to the lack of roads and the danger of land mines. Instead, the main reason to visit Phnom Kulen, 50km north of Siem Reap, is to gawp at the massive reclining Buddha carved out of a huge rock in the sixteenth century, though once you’re here you may find yourself more taken with the piety of the Buddhist devotees who come to worship at a chain of shrines.
You don’t need an Angkor entry pass to visit Phnom Kulen, but foreign visitors are charged a hefty $20 to visit the site; this, coupled with the cost of hiring a vehicle ($20–50, depending what kind of vehicle and who you hire it from), will keep all but the most dedicated explorers from visiting.
The area was heavily mined by the Khmer Rouge and although HALO are working there now, it has yet to be fully cleared, so you shouldn’t wander off to locations other than those described below unless you have an experienced local guide.